I have 33's churning with 4.63's...and I don't feel like I'd do a gear change to improve things...my cruising RPM is very relaxed now.
I'd do a low range t-case swap before I'd do a diff change.
If I was running 35+'s monster meats, and I was shuddering on take off and never got to use 5th...I might go and plunge towards 5.88's or something in that range...but it would have to really bug me.

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- TJ
2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....
Friends don't let friends drive stock.
http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif